I prefer not to use too much heat at all when evapping vinegar pulls. Comparative assays on the same batch of cactus have shown that the heated pull was less effective.

Distilling limonene can ve very useful. As you can easily distil it using just hot water as a heat source it's very unlikley that anything else in the limonene will be ditsilled over as well. Limonene is slightly vollatile and to the best of my knowledge, the impurities in cactus are not.